Sex differences in the blood metabolome of extremely preterm infants: a pilot study on the impact of antibiotic therapy.

BACKGROUND: Despite growing recognition of sex differences in medicine, little is known about their role in neonatology, particularly among extremely premature infants (EPI, < 28 weeks gestation), who face high morbidity and mortality driven by infections. Antibiotics therapy is widely used but may alter cellular metabolism, leading to adverse drug reactions. However, pharmacological studies in EPI remain limited, and sex-dependent effects of antibiotic treatments are largely unexplored. This study investigated sex-related metabolomic differences in EPI in relation to antibiotic exposure. METHODS: Targeted mass spectrometry (MS) was applied to dried blood spots (DBS) collected within the neonatal screening program of the Campania region (Italy) between 2018 and 2023. Amino acids (AA) and acylcarnitines (AC) were quantified in 116 EPI stratified by sex and antibiotics treatment. RESULTS: Untreated EPI of both sexes showed largely comparable metabolic profiles, with the exception of higher C16OH levels in males. Antibiotic treatment, however, markedly amplified sex-dependent divergence, with male EPI displaying significantly elevated AC concentrations (C0, C2, C3, C4, C5, C6, C5OH, C10:1, C16:1, C18, C18:1) compared to females. Stratification by penicillins + aminoglycosides treatment revealed distinct patterns: in EPI treated with a penicillins + aminoglycosides combination, males exhibited higher levels of C0, C2, C4, C6, C16:1, C18, and C18:1, while C3, C5, C5OH, and C10:1 no longer differed by sex. Furthermore, eight additional AC (C3DC, C14:1, C14, C16, C10DC, C16OH, C4OH, C16:1OH) were significantly elevated in treated males, differences that were not detected when all antibiotic classes were pooled. CONCLUSIONS: These findings demonstrate that standard empirical antibiotic therapies for prematurity exert sex-dependent effects on neonatal metabolism, with antibiotics amplifying AC alterations in males. Our results underscore the need to consider sex as a key biological variable in neonatal pharmaco-metabolomics and highlight the potential of metabolic profiling to optimize individualized treatments in EPI.